I played this game with Hummingbird, his friend, and his friend's mom. It took me about 1/3 of the game to get into the flow (mostly it felt like I was playing catch-up since the other three were all experienced Forest Shufflers). Once I got my bearings, I had so much fun. I expect I prefer the 4+ players group size to the 2-player option. I like that with more players everyone is mostly focused on building their own forest. I suspect with just two players it becomes (or can become) much more competitive. I like collaboration more than cooperation. This game wasn't exactly collaborative, but it was more like trying to do your best with the board/environment, not really about strategizing against other players.
Idea: a game like this, but where the players each build their own forest and have a collaborative goal. Use gift economy, where sharing openly is to everyone's mutual benefit. Set milestones like "have ___ established pollinators and ___ established angiosperms" "feed the bears enough salmon to survive hibernation" "have enough surviving salmon to populate the rivers next year" etc... Some resources are forest/biome specific, but others are necessary for all forests/biomes.